Manufacture of surface-active products



Aug. 20, 1957 F. T. E. PALMQVIST 2,803,635

MANUFACTURE OF SURFACE-ACTIVE PRODUCTS Filed June 2, 1954 4 Sheets-Sheet 2 750 np. m 600 r. p. m

3p/me 220 V INVENTOR free/rib ocz'ar (Emanuel @a/myvz'sz 8i: W am Aug. 20, 1957 F. "r. E. PALMQVIST 2,803,635

MANUFACTURE OF SURFACE-ACTIVE PRODUCTS Filed June 2, 1954 4 Sheets-Sheet 4.

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INVENTOI? ATTRNE Y5 United States Patent MANUFACTURE OF SURFACE-ACTIV E PRODUCTS Fredrik Teodor Emanuel Palmqvist, Stockholm, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application June 2, 1954, Serial No. 434,045

Claims priority, application Sweden June 12, 1953 11 Claims. (Cl. 260-413) The present invention relates to the manufacture of surface-active products containing salts of alkali metals, and nitrogen bases with fatty acids, sulphonic acids or alkyl sulphuric acids, in the latter of which the alkyl group can be substituted, these products being characterized by forming U-shaped electrolyte-content viscosity curves. The invention has particular reference to an improved method for regulating the supply to a treatment chamber of the components taking part in the prepara tion of the products.

When making such products it is of the utmost importance that the electrolyte content in the various production steps and in the ready productis kept within certain limits. In soap-making according to the old method (the so-called batch method) the composition of the soap mass is checked during the intermediate stages and in the final product by sampling and analyzing the samples. This often requires much labor and time, and the analyses are in many cases obtained at such a late stage that it is impossible to get any real use from them.

Attempts have been made, however, to determine the electrolyte content in soap by modified pH-measuring, For example, British Patent No. 578,278 and German Patent No. 722,289 describe modified pH-measuring methods for rapid determination of the electrolyte content, especially the alkali content, in soap. Methods have also been disclosed which use color change indicators in combination with a photoelectric cell for determining the alkalinity in soap. There is, however, a disadvantage common to these prior methods heretofore mentioned, in that on one hand a very complicated apparatus must be used which is apt to cause trouble and to give erroneous indications, and on the other hand this complicated apparatus in most cases must be served by a highly qualified staif.

In the experiments which led to the present invention it was found that in the products defined above the curve indicating the relation between the electrolyte content and the viscosity of the product is not constantly falling or rising throughout its course but takes the form of a U. This means that for a certain change in the electrolyte content the viscosity change as a rule is considerably greater than would be expected from knowledge of only the viscosities in two electrolyte contents lying on either side of the bottom of the U-curve, because it would nor mally be assumed that the connecting line between the two points in question on the electrolyte content-viscosity curve was constantly falling or rising. As a result of this fact it has proved to be possible, by means of com paratively simply measuring devices, to obtain strong and reliable indications of changes in the viscosity of the mass, when changes occur in the electrolyte content of the mass. The present invention, by making use of this ob servation, eliminates the inherent drawbacks of the methods previously employed for electrolyte determination in soap. p

The new method, which can advantageously be applied to the preparation of the above mentioned sulphonation and sulphatation products as well as to soap, is charac terized primarily in that the material present in the treat ment chamber is kept in a homogeneous condition by mixing and is caused to actuate a viscometer, the supply of the material components to the treatment chamber be ing regulated according to the indications of the viscometer in such a way that the mass in this chamber will have a composition corresponding to a previously determined part of one of the legs of the U-curve.

The invention is described in greater detail below, ref erence being made to the accompanying drawings in which Fig. 1, in the form of curves, shows the relation between the soda lye content in a certain soap mass and its viscosity after the saponification procedure; Fig. 2 is a diagrammatic view of a preferred form of apparatus for practicing the invention, showing a viscometer inserted in a circuit in a saponification stage and part of a dosing motor controlled by the viscometer; Fig. 3 shows this circuit and the dosing means diagrammatically and on a reduced scale; Fig. 4 is a curve showing the relation between the content of electrolyte (calculated as NaCl) and the viscosity of 65% soap once grained and having a low glycerine content; Fig. 5 shows an example of at Me- Rain-diagram, and Fig. 6 is a diagram showing a curve in which electrolyte-content is plotted against pressuredifierence. The viscosity values in Figs. 1 and 4 are stated as pressure diiference, measured in the apparatus shown in Figs. 2 and 3.

For illustrative purposes, the invention is described below in connection with the continuous making of soap, it being understood, however, that the invention is also applicable to discontinuous or batch processes and is not limited to the production of soap. When applied to soap-making, the new method can be used in the graining and fitting stages, in addition to the saponification stage proper. The following description refers, however, to the saponification stage, it being assumed that fat is saponified with lye. Analogous conditions apply to the graining as well as the fitting stages, as will be understood by those skilled in the art.

In continuous saponification, it is of great importance that the composition of the soap mass formed can be ascertained continuously. There must always be a certain excess of alkali to ensure that full saponification is obtained. On the other hand, too high an excess of alkali can have a delaying effect on the saponification because it causes graining. It is important, therefore, that the alkalinity is kept at a desired value which corresponds to a certain point of the electrolyte-content viscosity curve.

The curves shown in Fig. 1 have been determined by flowing a certain mass of soap at a temperature of C. and at a fixed rate through a pipe-line provided with throttle means in the form of plates, the pressure diflerence between two points in the pipe-line being measured. The pressure diff-erence thus obtained forms a measure of the viscosity of the soap mass. The determinations have been carried out in such a way that the soap content has been kept constant and the electrolyte content (i. e., the content of soda lye) has been varied. If the soap contents are diiferent, the curves assume different courses, as shown in Fig. 1. In addition to the fiow rate and temperature of the soap mass, the quantity and the character of the soap as Well as the electrolyte influence the specific form of the curves, although variations in these factors will not remove the generally U-shaped characteristic of the curves. In practice, it is preferred to first establish what pressure difference corresponds to the electrolyte content desired and then, in the course of the soap-making operation, to control the sure difference is kept constant.

In order that the method may give reliable results, it

necessary that the soap mass flowing past the viscometer be a homogeneous average of the mass present in the saponification or treatment chamber. This mass is therefore kept in agitation, which can advantageously be effected (in discontinuous as well as continuous methods) in such a way that the homogeneous soap mass is withdrawn through a pipe-line from the saponifying chamber and pumped back to this chamber. In this way, the viscosity-measuring can be effected in a pipe-line which forms part of the circuit and is situated outside the saponifying chamber. As the lye quantity is the smaller of the saponifying components, the quantity of fat fed per unit of time to the saponifyingehamberis preferably kept constant and the quantity of lye fed per unit of time-is varied. For similar reasonsthe quantityof neat soap fed per unit of time in the fitting operation, for example, iskept constant and the quantity of fitting electrolyte fed per unit of time is varied. In practice, the quantity of each of the reaction components fed per unit of time can be regulated in'such a way that the soap mass, in saponification as well as in fitting, is kept within the fitting zone in the so-called McBain-diagram. A more exact explanation of the latter is found in Bailey, Industrial Oil and Fat Products, New York 1945, page 625, and in the description of Fig. which will appear presently.

In Figs. 2 and 3, 1 designates the saponifying chamber proper which is provided with throttle plates 111 (Fig. 3), and 2 is a pipe-line through which a pump 3 feeds the material from the chamber 1 in circuit back into the same chamber. The pump 3 should be of a'type which feeds a'constant quantity per unit of time, e. g., a gear pump. Two pressure-sensitive means 4a and 4b are mounted in the pipe-line 2, preferably one on the suction side of the pump and one on the pressure side of the pump, as this will allow stronger indications to be obtained in the viscometer (i. 'e., higher pressure differences are obtained in the meter than if such means were placed on one and the same side of the pump). As shown, the pressure-sensitive means are membranes made of rubber, stainless steel, beryllium bronze, and other suitable flexible material. One side of each membrane 4a and 4b is exposed to the pressure of the soap mass in pipe 2 and the other side is exposed to and actuates a liquid mass 6 in a U-pipe 5. The liquid mass 6 may consist of a body of mercury 7 lying in the lower part of the U-pipe and surmounted by columns of water contacting the respective membranes. If the viscosity of the soap-mass passing through the pipe 2 increases, the pressure difference indicated by the mercury column in the U-pipe will rise. The desired pressure difference is determined by means of an adjustable electric contact member 3 which is fitted in the U-pipe. The contact 8 may consist of a small iron piece suspended within the U-pipe on a spirally wound metal wire 9, the winding of which has a tendency to contract so that the iron piece is drawn upwards in the pipe 5. The position of the contact 8 can then be controlled by a magnet 10 adjustably mounted outside the U-pipe, so that the contact is movable with the magnet to the level desired. The metal wire 9 is connected with a line 11 fused into the U-pi'pe and passing through its wall, and the mercury mass "7 in the U-pipe is in electrical contact with a line 12 inserted in a similar mannerv at the bottom of the U-pipe. The indications provided by such a pressurediiference meter are very strong and for that reason the meter can be used directly as an impulse emitter. This makes it possible automatically to adjust the alkalinity of'the soap to a desired value.

The viscometer may, of course, take other forms, such as a centrifugal pump connected in series with a liquidquantity meter, the latter indicating the viscosity.

According to Figs. 2 and 3, the dosing pump for the fat or saponifiable matter is driven by a constant speed motor 3.1,while the dosing pump 32 for the lye or saponifying agent is driven by a variable speed motor 21. The speed of the latter motor is controlled through its dual field windings by the circuitry shown in Fig. 2. As there shown, 13 designates a 3-phase 220- volt line with a three-pole main switch 14. Between two phases in the line 13 there is connected a 220/ 12 volt transformer 15, the low voltage side of which is connected between the line 12 and a line 16. A signal lamp 117 (or possibly an acoustic alarm) is connected between the lines 11 and 16. A relay 18 is connected in parallel with the lamp 17 in the same circuit. The relay 18 closes the circuit of a relay 19 which is connected between two phases in the line 13. The relay 19, when energized, closes a three-pole switch 20 which operates the motor 21 at its higher speed, as by connecting its field 21a to the power line 13 and thereby activating eight of the ten poles of the A. C. motor. At the same time the relay 19 opens a single-pole switch 22 in the circuit of a relay 23, which is' connected between two phases of the line 13. The relay 23 controls a threepole switch 24 which, when-closed, operates the motor 21 at its lower speed, as by connecting its field winding 21!; to the power line 13 and thereby activating all ten of its poles. Deenergizing of relay 23, by opening of switch 22, causes switch 24 to open and disconnect the high speed winding 21b from the power line while the low speed winding 21a is energized.

The mode of operation of the device is as follows: The saponification i effected at the left-hand part of the curves shown in Fig. 1, and as longas the viscosity of the soap mass flowing through the pipe 2 is low the mercury in the U-pipe 5 does not reach the contact member 8. The relays 18 and 19 are therefore deenergized, so that the switch 20 is open. The switch 22, on the contrary, is closed so as to close the switch 24 through the relay 23. Thus, the motor winding 21b is energized and the motor runs at its lower speed, say 600 R. P. M., whereas the motor winding 21a when energized operates the motor at its higher speed, say 750 R. P. M. This means that when the motor 21 is running at its lower speed the dye dosing pump 32 ha a throughput rate which is %g=% of full capacity When the motor 21 of the-lye dosing pump runs at the lower speed, the lye deficit therefore increases gradually so that a displacement to the'left is obtained in the diagram according to Fig. 1, that is, the viscosity increases. Consequently, the pressure drop in the pipe 2 increases and as a result the mercury column"! in the right-hand half of the U-pipe 5 rises to engage the contact member 8, whereby the relay 19 closes the switch'20 and at the same time opens the switch 22. This means that the high speed motor winding 21a is now energized from the line 13, while the low speed motor winding 21b is disconnected from the line 13 through deenergizing of relay 23. The lye motor 21 now runs at higher speed so that an increased lye quantity is fed. This gives a displacement to the right in the diagram of Fig. 1, that is, the viscosity of the soap mass is reduced. As a result, the mercury column 7 in the right-hand leg of the U-pipe 5 drops and breaks contact with the member'S, thereby restoring the lye motor to its low speed condition.

It will be apparent that according to Fig. 2, the righthand leg of the mercury column 7 provides a means for detecting deviations in the viscosity of the soap mass relative to a reference viscosity value (whichmay be represented, for example, by the height of the contact 8), since increasing viscosity causes this leg to rise and vice versa. While these deviations man be detected visually from the mercury column, and the rate of lye feed varied manually to counteract the deviations, the electrical control system including the contact 8 serves to vary the lye feed automatically'so as to maintain the material in the treatment chamber at approximately the composition corresponding 'saponification may cause the operation to reach the bottom part of the curve in Fig. 1, where the viscosity changes are small when the electrolyte content is changed. In such cases it is advantageous to add, besides the lye, another electrolyte (usually common salt) so that the operation reaches a steep part of the right-hand leg of this curve, thereby making it possible to use a quantity of soda lye suflicient for full saponification and at the same time obtain a satisfactory regulation. In this case, the desired operation of the lye control system can be obtained by moving the electrical control 8 and its adjusting magnet 10 from the right to the left side of the U-tube 5, so that the circuit 1112--16 is closed by a decrease in the viscosity or pressure difference and opened by an increase thereof.

The arrangement described above has been tried in practical operation and has proved to be thoroughly capable of keeping a desired constant composition (:0.005% electrolyte, absolute measure) of the soap mass present in the saponifying chamber.

In order to prevent excessive wear of the various electrical components, it is preferable that the relay 18 be of the delayed action type or to provide a separate delaying relay (not shown) which delays the operations of relay 19 in response to making and breaking of the contact 8. This prevents excessive hunting of the control system.

The viscometer as well as the controlling means of the lye dosing pump are chosen as examples only and can, of course, be replaced by other equivalent devices.

The curve shown in Fig. 4 refers to a soap mass at 90 C. suitable for manufacture of toilet soap. In the curve, the fitting zone lies between 0.84 and 1.25% electrolyte, calculated as NaCl, and covers thus the bottom part of the curve. In the fitting zone, neat soap is in phase-equilibrium with nigre. The so-called threephase zone in the McBain diagram lies between the electrolyte contents 1.25 and 1.35%, i. e., in this zone are neat soap, nigre and spent lye in phase-equilibrium with one another. The graining zone lies above 1.35% electrolyte content, i. e., neat soap is here in phase-equilibrium with spent lye. It is important to know the course of this curve when graining and fitting soap.

Fig. 5 is a McBain diagram for sodium soap of a pure fatty acid, i. e., lauric acid, at +90 C. On the diagram, the percentage of electrolyte (by weight), in this case sodium chloride, is marked on the abscissa, and the percentage of soap (also by weight) on the ordinate. The reading of the composition at a point of the diagram, point a, for example, is made by following the right-angle co-ordinates from the axes. Thus, the composition at point a is 2.0% sodium chloride, 41.0% sodium laurate (soap), and the balance up to 100% makes 57.0% water. On the diagram, the neat soap zone is marked A, the middle soap zone B, the nigre zone C, the graining zone D, and the fitting zone E. The first three zones represent homogeneous phases, whereas the last two represent inhomogeneous phases (mixed phases) made up of two components; the graining zone corresponding to a mixture of neat soap and spent lye, and the fitting zone to a mixture of neat soap and nigre. The other zones of the diagram are without interest in this connection and will not be further dealt with, other than to point out that F is a three-phase zone neat soap plus nigre plus spent lye, which is necessarily passed when displacing the soap composition from zone D to zone B; G is another three-phase zone neat soap plus nigre plus middle soap; and H is a two phase zone neat soap plus middle soap. The main part of the U-shaped curves previously mentioned lie within the zones D, E and F, although the left-hand upper part of these curves lies within the zones G and H.

When making soap according to the conventional method, the fat is saponified with soda lye of such a concentration that the composition of the soap formedv will lie within the area C, that is, in the nigre zone, for example, point a. Sodium chloride or sodium chloride solution is then added to the nigre, whereby the composition of the material passes over to the right into the graining area, for example, point b of zone D. As this zone represents an inhomogeneous phase, the material can be divided by separation into two pure phases, namely, a neat soap phase (represented by point e of zone A) and a spent lye phase of very low soap content, about 0.3 to 0.5%, and of high electrolyte content, about 14% (point d of zone D). The soap produced cannot yet be worked into a marketable product because it is not What is termed millable. The consistency is hard and the material is brittle, and the soap would not hold together on being stamped.

In order to obtain a millable soap, the grained neat soap must be fitted, which means that its composition, by adding water and a weak electrolyte, is displaced obliquely downward to the left on the diagram, into zone B. This zone, like the graining zone D, represents an inhomogeneous phase, so that the mass separates into two pure phases, one phase of fitted neat soap (corresponding to a point on the boundary line to the zone A) and a nigre phase (corresponding to a point on the boundary line to zone C).

Example 1 The process according to the invention is described below as performed in the arrangement according to Fig. 2 and applied to fitting of soap, since this operation presents the greatest difficulties to the person skilled in the art, who, to carry it out according to the methods commonly used heretofore, must have long experience and good judgment. The saponifying and graining operations are carried out analogously. The electrolyte in the following is calculated as NaCl, 0.87 kg. NaOH having the same graining effect as 1.00 kg. NaCl. Further, the quantities stated are calculated per hour.

1000 kg. of 70% neat soap are prepared from a raw fat such that the electrolyte-content pressure-difference curve of the soap agrees with the curve in Fig. 4, this soap coming from the graining stage of a continuously operating plant and having an electrolyte content of 0.65%. To this soap is dosed 14.9 kg. of a mixture of NaCl and NaOH having a graining effect corresponding to 20% NaCl-solution. The solution mixture used contains 4.35% NaOH and 15% NaCl. The dosing device which feeds in the electrolyte solution is of the type shown in Figs. 2 and 3 for feeding the lye. To adjust the soap mass to the desired soap percentage (65%), 62'

kg. of water per hour is added through a separate dosing device operating independently of the closing device for electrolyte solution. The soap mass thus formed gives a pressure difference of mm. Hg, i. e. the total electrolyte content becomes 0.88%. In this way the soap mass forms a mixture of neat soap and nigre consisting of 826 kg. 69.7% neat soap having an electrolyte content of 0.46%, and 251 kg. nigre having a soap content of 49.5% and an electrolyte content of 2.27%. This mixture is led to a centrifugal separator in which it is divided into neat soap and nigre. The neat soap is thereupon worked further in the common manner into" finished toilet soap.

Example 2 efficient of 2.00. The graining coefiicient of sodium hydroxide is 0.87. 1273 kg. of 18.85% sodium hydroxide solution (:240 kg. NaOI-I]l033 kg. H2O) was added to 1137 kg. sulphatedlauryl alcohol containing 1000 kg. lauryl sulphate, 109.5 kg. sulphuric acid, and 27.5 kg. water. Hereby is formed 2410 kg. solution of sodium lauryl sulphate containing 1082 kg. Na-lauryl sulphate (45%), 162 kg. NazSOr (6.73%) and 1166 kg. H2O (48.3%).

The diagram, Fig. 6, shows an electrolyte-content pressure-difference curve for a solution containing 45% Nalauryl sulphate. The electrolyte content is on the diagram shown as NaOH. The amount of NazSOa shown in the example has a graining effect corresponding to 2.93% NaOH. This amount of electrolyte excess corresponds to a differential pressure of 189 mm. Hg. means of the system described herein, the addition of neutralization agent is regulated through this differential pressure.

I claim:

1. In the preparation of surface-active products containing salts of alkali metals, and nitrogen bases with fatty acids, sulphonic acids, or alkyl sulphuric acids in which the alkyl group can be substituted, said products being characterized by forming U-shaped electrolyte contentviscosity curves, the improvement in regulating the supply to a treatment chamber of the components taking part in the preparation of the product therein, which comprises mixing the product to maintain it in a homogeneous condition, detecting deviations in the viscosity of the homogeneous product relative to a reference viscosity value, and l regulating the supply of the components to said chamber in accordance with the deviations thus detected to give the product a composition corresponding approximately to a predetermined part of one of the legs of the curve, the preparation of said product being carried out in the 7 zones bordering upon the neat zone of a McBain diagram.

2. The improvement according to claim 1, in which the mixing is carried out by circulating the product.

3. The improvement according to claim 1, in which the mixing is carried out by withdrawing the product from and returning it to the treatment chamber in a circuit, said detecting of the viscosity deviations being effected at a part of the circuit outside the treatment chamber.

4. The improvement according to claim 1, in which the product is led from the treatment chamber through an external flow path at a constant rate, said viscosity deviations being detected by measuring the pressure drop between two points in said flow path.

5. In the preparation of soap from saponifiable matter and a saponifying agent by feeding the same as reaction components to a treatment chamber in a saponification stage to form a soap product and thereafter feeding the soap and a further reaction component to another treatment chamber for further processing in a subsequent stage, wherein the soap product in each stage forms a U-shaped electrolyte content-viscosity curve, the improvement in supplying to the treatment chamber of at least one of said stages the components taking part in the preparation of the reaction product therein, which comprises mixing the reaction product to maintain it in a homogeneous condition, detecting deviations in the viscosity of the homogeneous product relative to a reference 8 viscosity value, and regulating the supply of the components to said chamber in accordance with the deviations thus detected to give the product a composition corresponding approximately to a predetermined part of one of the legs of said curve, the preparation of the soap being the rate of feed of the reaction components to said cham-. ber in the saponification stage is regulated to keep the soap productin said last chamber within the fitting zone of the McBain-diagram.

8. The improvement according to claim 5, in which said subsequent stage isa graining stage wherein the supply of the reaction components to the treatment chamber is regulated as defined in claim 5.

9. The improvement according to claim 5, in which said subsequent stage is a fitting stage wherein the supply of the reaction components to the treatment chamber is regulated as defined in claim 5.

10. The improvement according to claim 5, in which said further reaction component is an electrolyte, the soap being fed to the chamber of said subsequent stage at a constant rate, and the feed of the electrolyte to said last chamber being regulated as defined in claim 5.

11. In the preparation of a surface-active product characterized by forming a U-shaped electrolyte content-viscosity curve, by feeding to a treatment chamber the components taking part in the preparation of the product, the improvement in regulating the supply of said components to the chamber, which comprises mixing the product to maintain it in a homogeneous condition, detecting deviations in the viscosity of the homogeneous product from a reference viscosity value corresponding to a predetermined part of one of the legs of said curve, and regulating the supply of the components to said chamber to counteract the deviations thus detected and thereby maintain the product at a composition corresponding approximately to said part of the curve, the preparation of said product being carried out in the zones bordering upon the neat zone of a McBain diagram;-

References Cited in the file of this patent UNlTED STATES PATENTS 2,594,461 Ledgett Apr. 29, 19.52

FOREIGN PATENTS 578,278 Great Britain July 21, 1946 OTHER REFERENCES McBain et a1.: J. Chem. Soc., London (1927), pages Davidsohn et al.: Soap Manufacture, vol. 1 (copyright 1953), pages 29-30. 

1. IN THE PREPARATION OF SURFACE-ACTIVE PRODUCTS CONTAINING SALTS OF ALKALI METALS, AND NITROGEN BASES WITH FATTY ACIDS, SULPHONIC ACIDS, OR ALKYL SULPHURIC ACIDS IN WHICH THE ALKYL GROUP CAN BE SUBSTITUTED, SAID PRODUCTS BEING CHARACTERIZED BY FORMING U-SHAPED ELECTROLYTE CONTENTVISCOSITY CURVES, THE IMPROVEMENT IN REGULATING THE SUPPLY TO A TREATMENT CHAMBER OF THE COMPONENTS TAKING PART IN THE PREPARATION OF THE PRODUCT THEREIN, WHICH COMPRISES MIXING THE PRODUCT TO MAINTAIN IT IN A HOMOGENEOUS CONDITION, DETECTING DEVIATIONS IN THE VISCOSITY OF THE HOMOGENEOUS PRODUCT RELATIVE TO A REFERENCE VISCOSITY VALUE, AND REGULATING THE SUPPLY OF THE COMPONENTS TO SAID CHAMBER IN ACCORDANCE WITH THE DEVIATIONS THUS DETECTED TO GIVE THE PRODUCT A COMPOSITION CORRESPONDING APPROXIMATELY TO A PREDETERMINED PART OF ONE OF THE LEGS OF THE CURVE THE PREPARATION ON SAID PRODUCT BEING CARRIED OUT IN THE ZONES BORDERING UPON THE NEAT ZONE OF A MCBAIN DIAGRAM. 